Electric control apparatus for fuel burners



Dec. 3, 1935. A. l.. RUBEL l 021825 ELECTRIC CONTROL APPARATUS FOR FUELBURNERS l Filed oct. 16, m53

RELAY SWITCH latenleol Dec. 3, 1935 ELECTRICI CONTROL APPARATUS FOR FUELBURNERS Abraham L. Rubel, Des Moines, Iowa, assignor to Penn ElectricSwitch Co., Des Moines, Iowa, a

corporation of Iowa Application october y1e, 193s, serial No. 693,800

2 Claims.

An object of my present invention is to provide control apparatus forthe electric circuit of a fuel burner, such apparatus being of simpleconstruction and operable to automatically take 5 care of variousemergencies arising during the operation of the burner.

A further object is to provide an automatic controller-including acombustion switchV which is opened when combustion occurs in order tobreak the circuit through a lock-out switch so that upon combustionoccurring the lock-out switch will not thereafter lock out.

Still a further object is to provide control apparatus including a roomthermostat operated relay which normally initiates and terminatesoperation of a fuel burner and which initiates operation of ignitionmechanism for the fuel burner, termination of the operation of theignition mechanism being eected by an ignition trip mechanism which inturn is operated by a combustion switch, the combustion switch includinga lost motion connection to delay the operation of the ignition tripmechanism.

A further object is to provide control apg; paratus including acombustion switch having a friction connection for one of the movablecontacts and a lost motion connection which provide for de-energizingthe relay and re-cycling by re-establishing the starting circuit,respectively, so that between relay de-energization and re-cycling apurging period is provided, thus allowing the combustion chamber of afurnace or the like to be cleared of dangerous gases by the naturaldraft therein before the ignition mecha.-

'35 nism is re-energized by establishment of the starting circuit andthus eliminating an explosion upon such re-energization.

Another object is to provide a control structure in which ignitioncontacts are normally closed, but the ignition current does not flowthrough them until a room thermostat is also closed, these contactsbeing so mounted on aJ tacts of a combustion switch which have thepeculiarity of closing only after the combustion switch moves from coldto hot position and then starts to return toward cold position, suchpeculiarity being elected by a frictional mounting 5 for one of thecontacts of the switch.

With these and other objects in view my invention consists in theconstruction, arrangement and combination of the various parts of mydevice, whereby the objects contemplated are 10 attained, as hereinaftermore fullyi set forth, pointed out in my claims, and illustrated in theaccompanying drawing, in which:

Figure 1 is an electrical diagrammatic view of an electric controlapparatus for fuel burners'15 embodying my invention.

Figure 2 is a simplified wiring diagram of the same.

Figure 3 illustrates different successive positions of a combustionswitch shown in Figure 1. 20 Figures 4 and 5 are different successiveviews of the relay switch shown in Figure 1 during its operation.

Figure 6 is a sectional View on the line 6 6 of Figure 1 showing detailsof a combustion switch 25 which I employ; and

Figure 7 is a front view of the ratchet and lost motion mechanism of thecombustion switch.

On the accompanying drawing, a plurality of contacts are illustrated.Lock-out switch con- 30 tacts are shown at Ill. A relay switch has motorcontacts I2 and I4, ignition contacts I6 and holding contacts I8. Therelay switch includes an ignition trip mechanism having contacts 20.

A combustion switch is provided with ignition trip contacts 22, relayde-energizing contacts 24 and starting contacts 26.

The lock-out switch alsoincludes a cam 28 spring actuated to separatethe normally closed contacts Ill but normally held from doing so by4 abimetal latch 30. The latch 3l! is adapted to be warped to unlatchedposition by a lock-out switch heater 32 when it is hot.

The relay switch includes a relay coil 34 divided into two separatecoils 34a.` and 34h by a central connection. An armature 35 normallyheld spacedfrom the coil 34 is adapted to be attracted thereby whenthecoil is energized. A bridge piece 38 carried by the armature 36 connectsone of the contacts l2 with one of the 50 contacts I4, when the relay isenergized as in Figure 4, thereby eliminating a pig-tail connection.

ture 36 to the position of Figure 1. spring 42 carries one of thecontacts I6.

An ignition trip mechanism is provided in the relay switch and includescontacts 26 and 26a. The contact 26a serves as an armature for anelectromagnet 44.

The contact 26a retains the contacts I6 engaged as in Figures 1 and 4whether the relay is'or is not energized providing the electromagnet 44is not energized and permits them to separate providing the relay isenergized and the magnet is then energized.

The combustion switch includes a rotatable rod 46 and a bimetal coil 48responsible to temperature in the combustion chamber of a furnace. Oneend of the coil 48 is secured to the rod 46 as at 41 and the other endis stationarily anchored as at 49 to a housing 5I for the combustionswitch. 'Ihe combustion switch also includes a toothed disk 52 and alost motion connection between the rod 46 and the toothed diskcomprising an arm 56 on the rod and spaced stops 54 on the disk. Thedisk 52 is rotatably mounted on the rod 46. A leaf spring 56 carryingone of the contacts 26 is adapted to coact with the periphery of thetoothed disk 52 to be operated thereby during rotation thereof suchcooperation being shown in Figure 7; lthe free end of the spring 56tends to remain in the position of Figure 3 (A) and the full lineposition of Figure 7 so that, due to its path of movement describing anarc 53, it can be swung immediately upon the toothed disk beginning torotate and after a predetermined degree of rotation permits the teeththereof to slip past it as in Figure 1 and Figure 3 (C).

The combustion switch further includes a frictional mounting comprisinga plate 58 for one of the contacts 24, the arm carrying this contact andalso the arm carrying the upper contact 22 being actuated from the leafspring 56. All of the arms carrying the contacts 22, 24 and 26 are leafsprings except the one carrying the upper contact 24 and having theplate 58 which can be of rigid material and pivoted at 6I. The plate 58is caused to frictionally engage the insulating block 55 whichindirectly supports the contacts 22, 24 and 26 by means of a springwasher 59 on the pivot 6 I.

A transformer 66 is provided for furnishing current for the relay coil34, the lock-out switch heater 32 and the ignition trip magnet 44.

Terminals L and L for line wires, I for ignition mechanism, M for motorand R and R for a room thermostat or main control switch, areillustrated in Figure 1. These are also illustrated The leaf in Figure 2and a motor, ignition mechanism and a room thermostat are indicated asMotor, Ign. and Room therm., respectively. The primary and secondary ofthe transformer 66 are indicated at Pri. and Sec..

Practical operation The circuit connections with the various coils,heaters, contacts, etc., are all fully shown in Figures 1 and 2. 'I'heparts in Figure 1 and the contacts in Figure 2 are in normal ornon-operating position.

Starting circuit ing contacts 26 of the combustion switch to the upperend of the transformer secondary.

This causes the armature 36 to be attracted whereupon its contacts I2,I4 and I8 are closed and I6 are held closed or in their normal position5 by the ignition trip armature 26a as shown in Figure 5. N

The closing of the contacts I2 and I4 establishes both the motor circuitand the ignition circuit from the terminal L through the lock-out l0switch contacts I6, the contacts I2 and I4 and the contacts I6 which arealready closed. Closing of the holding contacts I8 provides a holdingcircuit for the relay which is energized under certain circuitconditions. 15

Running circuit If combustion occurs, the starting contacts 26 will rstbe opened by reason of the bimetal coil 48 slightly rotating the tootheddisk 52, as shown 20 in Figure 3 at A. This breaks the starting circuit,but permits the current from the upper end of the relay coil 34a to owthrough the coil 34h and the holding contacts I8, thus holding the relayin its energized position. Passage of the 25 current through the coil34h, instead of the shunt circuit including theA contacts 26, reducesthe current so that the lock-out switch heater 32 will not become hotenough to trip the lock-out switch to open circuit position. 3o

If combustion does not occur, then the secondary current from thetransformer 66 will be oi higher value because it is choked only by thecoil 34a and not by the coils 34a and 34h so that the heater 32 willheat up suiliciently to trip the 35 lock-out switch.

If combustion does occur,the running circuit just described willnormally be maintained until the room thermostat opens it because of arise of the temperature in the room to a predetermined degree.

Ignition trip circuit This circuit may be traced from the terminal Rthrough the ignition trip de-energizing con 45 tacts 26 and 26a, themagnet 44 and the ignition trip contacts 22 of the combustion switchwhen they close. It is desirable to.A have them close after a delayedperiod of time however. Ac-

cordingly, the spring arm 56, due to its tendency to assume asubstantially central position will move the toothed disk 52 to theposition of Figure 3 at A after the arm 56 of the combustion switchmoves from cold toward hot position, the left stop pin 54 following itby reason of the arm 55 56 rotating the toothed disk 52 until theposition at A is assumed, whereupon the arm 56 will move from the leftstop pin to the right one. After it engages the right one, as at B, bothcontacts 24 will be moved downwardly but will not become 30 engaged.

Finally, the contacts 22 will become engaged, thereupon energizing theignition trip magnet 44 and attracting the armature 26a. This willpermit the spring arm 42 of the relay switch to o5 spring upwardly fromthe position of Figure 4 to the'- position of Figure 5, the contacts 26and 26a during this operation becoming separated so that after ignitiontrip occurs, current will no longer flow through the ignition tripcircuit.

Failure of combustion after establishment After combustion has once beenestablished, if it should fail for any reason, the combustion switchwill move from the hot position of Fig- 75 mc s ci o back through thepcciucns D. n F and G to the cold position of Figure l. Y

In the D position, the arm 50 has moved counter-clockwise and the spring-56 has caused the right stop pin 54 to follow it, first separating theignition trip contacts 22 so that they are in initial position. Furthermovement, as at E,

will permit the spring 56 to allow the lower contact 24 to contact withthe upper one, thus establishing a relay de-energizing circuit by reasonof the contacts 2l shunting. the-relay coil 34. This opens the motorcontacts I2 and Il, thus de-energizing thefmotor and the ignitionmechanism and opens the holding contacts I8, thus placing them all -inposition as for initial opera-i tion.

v When ,the armature 36- of the relay switch moves to its initialposition, the bridge piece 3Q engages the arm lll of the leaf spring I2,pulling it from the position of Figure 5 tothe position of Figure 1,thereby permitting the armature 20a to assume its position'of Figure 1to hold the contacts le engaged when the relay is again energized` asin- Figure 4.

The combustion switch then moves to the position of F in Figure 3, thearm 5l swinging from the right hand stop pin 5l toward the left one y toprovide a time period in which purging can occur. Finally the contacts2l will be opened, as at G, and then the contacts 26 will be closed asin Figure 1. Upon such closing of the contacts 26, the controllerre-lnitiates the starting circuit, thus re-cycling the burner. 'I'heburner will recycle two or three times if it cannot operate properlyafter one purging period, whereupon the successive heatings of thelock-out switch heater 32 will be sumcient to trip the lock-out switch.The trouble must then be remedied and Aout departing from the realspirit and purpose of my invention, and it is my intention to cover bymy claims, any modified forms of structure or use of mechanicalequivalents which may be reasonably included within their scope. 5

I claim as-my invention;

1. A control system for a fuel burner having a motor controlled fuelfeeding means andignition mechanism comprising in circuit, a maincontrol switch, a first relay having contacts conlo trolling the motorcircuit and a holding circuit for said relay which are .closed only whenthe relay is energized and ignition contacts which are closed when therelay is de-energized, a second relay controlling trip mechanism whichwhen energized permits said ignition. contacts to open and a combustionresponsive switching mechanism having flrst contacts controllingenergization of said first relay which arepclosed in the absence ofcombustion and open immediately after combustion is obtained, secondcontacts controlling energization of said second relay which are closedin the; presence of combustion and which open immediately upon cessationof` combustion and third contacts which close and remain closed for atime period subsequent to the opening of the second contacts and Vthenopen prior to the reclosing of the first contacts, said third contacts,when closed, eifectuating dieenergization of said first relay. 2. Acontrol system for a fuel burner 'ving a motor controlled fuel feedingmeans and tion mechanism comprising in circuit, a main control switch, arst relay having contactscontrolling the mctcr circuit which cre c1oscaonly when the 3-5 relay is energized and ignition contacts which areclosed when the relay is de-energlzed, a sec ond relay controlling tripmechanism; which when energized permits said ignition contacts to openand a combustion responsive switching 40 mechanism having iirst contactscontrolling energization of said first relay which are closed in the Yabsence of combustion and open immediately after combustion is obtainedand second contacts' controlling energization of said second relay whichare closed in the presence of combustion and which open immediately uponcessation of combustion.

ABRAHAM L. RUBEL.

